Personally, I wouldn't try get 'serious value' out of them. If there are just a couple of these domain names, redirect them to your main site. But focus on getting serious value out of your main site instead. If you have great content for ChairtypeA it should be on your ChairtypeA page, not on a micorsite.
If you gain inbound links, best they point to your main site pages. Not to microsites. You're diluting the potential of ChairtypeA by spreading its content over 2 sites.